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Thread: VGA card with decent palette grayscaling for Gas-Plasma panel?

  1. #11
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    2,381

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    ... And just for laughs, here's one that does a palette swap on all 256 colors on the 320x200x256 graphics mode. Again curious if it has *any* affect on the attached plasma.

    Code:
    SCREEN 13
    CLS
    
    C = 0
    FOR x = 0 TO 15
    FOR y = 0 TO 15
    LINE ((20 * x), (10 * y) + 20)-(((20 * x) + 20), ((10 * y) + 30)), C, BF
    C = C + 1
    NEXT y
    NEXT x
    
    PRINT "Beginning swap cycle"
    
    DIM Blue AS LONG
    DIM Green AS LONG
    DIM Red AS LONG
    
    DIM palColor AS LONG
    
    FOR COL = 0 TO 255
    FOR Blue = 0 TO 63 STEP 16
    FOR Green = 0 TO 63 STEP 16
    FOR Red = 0 TO 63 STEP 16
    
    palColor = (Blue * 65536) + (Green * 256) + Red
    
    PALETTE COL, palColor
    
    NEXT Red
    NEXT Green
    NEXT Blue
    NEXT COL
    
    palColor = 0
    PALETTE 15, palColor
    
    PRINT "Finished"
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  2. Default

    Screen shots attached.

    Fahr1280_64colPalette_IntExt.jpg

  3. Default

    Why in the world does this forum not allow editing of my own posts beyond a few minutes? So very annoying. I don't like not being able to correct errors.

  4. #14
    Join Date
    May 2011
    Location
    Outer Mongolia
    Posts
    2,381

    Default

    Quote Originally Posted by Dagwood View Post
    Screen shots attached.

    Fahr1280_64colPalette_IntExt.jpg
    So I'm guessing there was no change at all on the plasma while the program was actually running? (The colors didn't flash or shimmer in any way?) That plus the fact that you can't distinguish the 16 horizontal color cells seems to confirm that the only thing you have to work with is a 4 bit nibble of raw from-memory pixel information and the palette is indeed not in the loop at all. Did you try the one that runs in 80 column text mode and verify that it also doesn't cause any change on the plasma at all? (I suppose it's remotely possible that the feature connector could be north of something that can shuffle palettes in the 4-bit modes, but I'm pretty skeptical about that.)

    I dug up the datasheet for the CT65540/65545, which has a dedicated on-chip flat panel interface module, and on page 180 it describes the dither options available. (Skimming it it looks like it can fake at least 60-ish shades of gray on a 4 bit panel.) I suspect to get better than what you're seeing you'll need a card with a chip like that. What I'm not entirely clear on from the datasheet is how exactly it translates the RGB shades in the palette register to the available dithers, but at least it does have the hardware to pay attention to the upper bits of an 8-bit pixel instead of ignoring it entirely.
    My Retro-computing YouTube Channel (updates... eventually?): Paleozoic PCs

  5. #15

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    Quote Originally Posted by Dagwood View Post
    Why in the world does this forum not allow editing of my own posts beyond a few minutes? So very annoying. I don't like not being able to correct errors.
    The powers that be are afraid you will say something monumentally important and then get mad and go back and delete it, thus depriving the world of whatever.

    Absurd, IMO, but it's been discussed several times and they are not open to changing it.

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